This project will continue to investigate the general phenomenon of shared antigenic components between microorganisms and neoplastic cells. Emphasis will be placed upon studying the importance of this observation with respect to possible prophylactic and therapeutic effects of microorganisms against tumors with which they share antigenic components. Similarities between some organisms and tumor antigens have already been observed and these observations will be the basis for additional studies using a variety of human and animal tumors which are now available. Sera from serial bleedings of tumor-bearing humans and animals, obtained at various stages of disease, will be tested for their capacity to bind bacterial and, if possible, tumor antigens. The precise function, if any, of tumor antigens that are shared with mycobacteria and with other microorganisms is not clear. In view of the widespread crossreactivity between BCG and other microorganisms, the identification of shared antigens between tumors and various organisms may provide valuable information for immunotherapeutic programs. Because of the universal presence of antibodies in human sera to mycobacteria and other bacteria, the possibility that effective immunologic responses to some tumor antigens depend in part on a preexisting state of sensitization to microorganisms merits serious consideration. BIBLIOGRAPHIC REFERENCES: Minden, Percy, Farr, Richard S. and Trembath, Joyce: Some variable controls for accurate heterologous anti-immunoglobulin (HAI) tests. Immunochemistry, In press 1975. Schumacher, M.J., McClatchy, J.K., Farr, R.S., and Minden, P.: The primary interaction of antibody to components of Alternaria. I. Immunologic and chemical characteristics of two nonprecipitating antigens. J. Allergy and Clin. Immunol., in press 1975.